Method of segregating temperature responsive circuit breakers according to their opening temperature

ABSTRACT

Circuit breakers are inserted into close fitting holes in a rotatable ring shaped metal block. The block is heated and maintained at a predetermined temperature that exceeds the normal opening temperature of the circuit breakers. At the time of insertion, the lead-in wires of each circuit breaker are clamped by a suitable device. When the circuit breaker thermostatically opens, the clamp releases and the circuit breaker falls from the block. The time interval between insertion and release permits segregation of the circuit breakers according to their opening temperature.

United States Patent Perkins [4 1 May 14, 1974 METHOD OF SEGREGATINGTEMPERATURE RESPONSIVE CIRCUIT BREAKERS ACCORDING TO THEIR OPENINGTEMPERATURE 3,409,127 11/1968 Aiken 209/81 R X Primary Examiner--RichardA. Schacher Attorney, Agent, or FirmJames Theodosopoulos [57] ABSTRACTCircuit breakers are inserted into close fitting holes in a rotatablering shaped metal block. The block is heated and maintained at apredeterminedtemperature that exceeds the normal opening temperature ofthe circuit breakers. At the time of insertion, the leadin wires of eachcircuit breaker are clamped by a suitable device. When the circuitbreaker thermostatically opens, the clamp releases and the circuitbreaker falls from the block. The time interval between insertion andrelease permits segregation of the circuit breakers according to theiropening temperature.

1 Claim, 3 Drawing Figures METHOD OF SEGREGATING TEMPERATURE RESPONSIVECIRCUIT BREAKERS ACCORDING TO THEIR OPENING TEMPERATURE BACKGROUND OFTHE INVENTION 1. Field of the Invention This invention relates tothermostatic circuit breakers and is particularly concerned with methodsof segregating such devices according to their opening temperature.

2. Description of the Prior Art Circuit breakers of the type with whichthis invention is concerned are shown in US. Pat. Nos. 3,272,944,3,278,705, 3,278,706, 3,307,126, 3,555,478,

3,573,697, 3,597,838 and 3,619,534. Such circuit breakers include a pairof normally closed electrical contacts, one of which is mounted ona'thermostatic element which deflects and opens the contacts when heatedto a predetermined temperature.

As pointed out in U.S. Pat. No. 3,597,838, it is usually not possible toconsistently manufacture a large number of circuit breakers all of whichwill open within a narrow predetermined temperature range. Accordingly,it is usually necessary to test each circuit breaker to determine itsopening temperature.

Prior art methods of testing, such as ovens or heated oil baths, aregenerally time consuming, expensive and not readily adaptable to highspeed manufacturing processes. For example, if circuit breakers havingan opening temperature between, say, 100 to l C are desired for aparticular application, the use of two oil baths would be required, onemaintained at 100C and the other at 110C. A group of circuit breakerswould first be inserted into the 100C bath and those that opened wouldbe set aside. The remaining ones would then be placed into the l 10Cbath and those not opening within a certain time interval wouldsimilarly be set aside. The remaining circuit breakers would then havean opening temperature within the range of 100 to l 10C.

It is an object of this invention to provide a rapid, clean method ofsegregating circuit breakers according to their opening temperature.

SUMMARY OF THE INVENTION This invention is applicable to thermostaticcircuit breakers that are enclosed within a substantially cylindricalcontainer, either a glass envelope. or a metal case, and which have twolead-in wires extending from one end of the circuit breaker. Theapparatus for testing the circuit breakers includes a horizontallypositioned, ring shaped, metal block having high thermal conductivity,which is rotatable about its axis, and which contains a plurality ofuniformly spaced vertical holes extending through the block. The blockis heated, preferably electrically, and has suitable controls capable ofmaintaining the block at a suitable predetermined temperature. To obtainclose temperature control, the external surface of the block arethermally insualted.

Circuit breakers are individually loaded into the holes in the block andare clamped therein by means of the lead-in wires. The clamps areelectrically operated in such a manner that they release uponthermostatic opening of the circuit breakers, thereby permitting eachcircuit breaker to fall through the hole into a suitable containerdisposed therebeneath.

In order to provide good heat transfer between the block and'the circuitbreakers, the holes in which the circuit breakers are disposed arefairly close fitting but are not so small as to prevent the circuitbreakers from falling through under the action of gravity. Also, thethickness of the block is greater than the length of the circuitbreakers so that the entire length of each circuit breaker is completelysurrounded by the heated block for efficient heat transfer with minimumcooling at the ends of the circuit breaker. For this purpose, thethickness of the block exceeds the circuit breaker length by at leastabout three circuit breaker diameters.

In operation the block is heated and maintained at a temperature thatexceeds the nominal opening temperatures of the circuit breakers beingtested. As the block is rotated, circuit breakers are loaded and clampedinto each hole. Disposed beneath the holes are a plurality of trays orchutes arranged so as to catch the circuit breakers as they release andfall from the block. The time interval between loading and release isrelated to the opening temperature of the circuit breakers and permitssegregation thereof according to ranges of opening temperature.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 isa plan view of apparatus forsegregating circuit breakers in accordance with this invention, showinga ring shaped block and holes therein.

FIG. 2 is an expanded sectional view of a circuit breaker within one ofthe holes.

FIG. 3 is a schematic representation of the electrical circuit thatcloses and opens the clamps for the circuit breaker lead-in wires.

DESCRIPTION OF THE PREFERRED EMBODIMENT Apparatus for segregatingcircuit breakers in accordance with this invention included a castaluminum ring shaped block 6 having an outer diameter of 48 inches, aninner diameter of 45 inches and a thickness of 2 inches. There were 200equally spaced holes 8, five-sixteenths inch diameter, drilled throughthe block.

Attached to the outer periphery of the block were eight 250 watt heaters14; the external surfaces of the ring and heaters were thermallyinsulated. Four electrical temperature controls were used which werecapable of maintaining a uniform temperature throughout the block to atolerance of plus or minus 0.75C.

Type SB glass enclosed circuit breakers 4 were tested and segregated.Said circuit breakers have a diameter of nine thirty-seconds inch, alength of 1 /4 inches, a current rating of 15 amperes and a nominalopening temperature range of to C.

The circuit breakers 4 were automatically loaded into the holes 8 of theblock 6, lead-in wires 18 up, while the block 6 was rotating at the rateof one revolution per 2 minutes, which is equivalent to testing 6,000units per hour. Each circuit breaker entering a hole tripped a switchwhich energized a solenoid 16 and activated a pair of clamps, one foreach lead-in wire. The clamps 10 supported the circuit breaker withinthe hole and were electrically operated to release when the circuitbreaker opened, thereby permitting the circuit breaker to fall throughthe hole.

Disposed beneath the holes around the periphery of the block were aplurality of chutes 12 which segrecuit breakers having an openingtemperature between 77 and 89C, the block temperature was maintained at107C. All circuit breakers that were released 28 to 45 seconds afterloading were within this desired opening range. I

The temperature at which the block is maintained is determined by thedesired opening temperature range for the circuit breakers. If a narrowtemperature range is desired, say, 105 to 110C, the block temperaturewould be set slightly higher, say, 115C, in order that the rate ofheating the circuit breakers be relatively slow. if a wider openingtemperature range is desired, say, 95 to 110C, then the heating rate.can be faster and the block temperature can be set at a relativelyhigher temperature, say, 120 or 125C.

1 claim:

1. A method of segregating normally closed thermostatic cylindricallyenclosed circuit breakers according to their opening temperaturecomprising the steps of:

collecting said circuit breakers in containers ar-' ranged to segregatethem according to the time interval between loading and release thereof.

1. A method of segregating normally closed thermostatic cylindricallyenclosed circuit breakers according to their opening temperaturecomprising the steps of: inserting said circuit breakers into closefitting holes in a heated rotatable ring shaped metal block; clampingthe lead-in wires of said circuit breakers to support them within saidholes; rotating said block while said circuit breakers are being heatedthereby; releasing said circuit breakers when the thermostatic elementsthereof open, thereby causing said circuit breakers to fall out of saidblock; and collecting said circuit breakers in containers arranged tosegregate them according to the time interval between loading andrelease thereof.